This invention relates to a modulation device for laser radiation, having at least one modulation means which can change at least in part the laser radiation which passes through the modulation device.
Modulation devices of the aforementioned type have been known for a long time. They can be used in different applications. Here for example laser printers, laser television, or even workpiece machining by laser radiation are to be named.
A typical modulation means used in the past is a so-called GLV modulator. Such a GLV modulator is operated in reflection. On its reflecting surface it has a whole number of crosspiece-shaped segments which are located parallel to one another and which can reflect the laser radiation. Each of these segments can be tilted in a concerted manner. Modulation occurs generally by two segments which are directly adjacent to one another being tilted differently or one of the segments being tilted and the other being left in its original position so that a small phase difference between the two adjacent component rays which are incident on these segments is formed by this different tilting of the two adjacent segments. This phase difference by direct interference in the area of the modulator leads to the propagation characteristic of the light which has been reflected by the modulator being able to be changed in a concerted manner.
The disadvantage here is the fact that intensely coherent light must be present for this purpose. In general, this is especially not the case in laser diode bars due to the extension of the individual emission sources of such a laser diode bar in the direction of arrangement of the emission sources (in the slow axis). Furthermore, it is also disadvantageous here that by the aforementioned peculiarity of the light emerging from a laser diode bar generally more than two adjacent, especially four or six segments adjacent to one another are illuminated, so that the resolution of such a modulation means is extremely poor. Furthermore, the individual states for the adjacent segments which are tilted toward one another and for the adjacent segments which are not tilted to one another, that is, the segments of a corresponding component area of the GLV modulator, can only be inadequately distinguished when a laser diode bar or a stack of laser diode bars is used as the laser source.
An object of this invention is to devise a modulation device of the initially mentioned type which is made more efficient, especially when using a laser diode bar or a laser diode stack as the laser light source.